The present invention relates to a device for influencing the starting of an internal combustion engine of a motor vehicle that has an electronically controlled gearbox, an electrically acting interlock that prevents the internal combustion engine from being put into operation when a gearbox status causing a driving force connection is selected, and a starter with an electromagnetic disengagement switch that is suppliable with battery current from an ignition switch during actuation of the starter.
In vehicles with automatic gearboxes currently in series production, a starting interlock is provided which is intended to prevent the engine from being started in any of the driving positions "R", "D", "3", "2" or "1" of the selector lever of the automatic gearbox. As shown in FIG. 4, the starting control conductor 18 for the magnetic switch 14 of the starter 13 is generally led from the ignition switch 17 to a so-called starting interlock switch 20, which is only closed in the selector lever positions "P" and "N". From the starting interlock switch 20, the starter engagement conductor 22 leads through a sealing location 23 in the engine compartment to the magnetic switch 14 of the starter 13. The starter 13 can therefore only be initiated and, in consequence, the internal combustion engine can only be started if the interlock switch 20 is closed, i.e., if the selector lever is located in one of the positions "P" or "N".
The starting interlock switch is generally located on the selector block of the selector lever or on the automatic gearbox. The arrangement of the selector lever on the gearbox has the advantage that transmission tolerances between the selector lever and the gearbox actuation cannot lead to starting in a driving position of the gearbox. Starting interlock switches which are arranged directly on the selector plate in the automatic gearbox are also known. This also makes it possible to exclude transmission tolerances, between the gearbox actuation and the elements of the selector plate determining the gear, as a possible cause for erroneous starting of the internal combustion engine with a force connection in the drive train.
This is, however, problematic if the interlock switch becomes defective by its contact elements welding together, for example. A switch then permanently "closed" in such a way means that the internal combustion engine can be started with force connection in the gearbox. This condition is particularly critical because the error can only be discovered when the dangerous situation has already occurred (a so-called "sleeping fault"). Another result with respect to the electrical installation in the vehicle is the requirement to lay a relatively thick conductor which is capable of carrying the high current of the magnetic switch on the starter from the ignition switch out of the passenger compartment to the gearbox or to its gear-selection control. Because vibration zones have to be bridged over in this process, laying a corresponding conductor requires correspondingly more attention and time as the conductor becomes thicker and, in consequence, stiffer. In the case of the variant which is most tolerant to faults, in which the starting interlock switch is arranged in the gearbox, this conductor, which is therefore looped into the gearbox, must be protected in a particularly complicated manner against short circuit and ground short.
U.S. Pat. No. 1,231,637 describes a mechanically acting device for avoiding a simultaneous driving force connection between the internal combustion engine and the driving train and between the internal combustion engine and the starter such that intervention in the starter is impossible when the first-mentioned connection is made.
U.S. Pat. No. 4,033,311 describes an electronic ignition system for the internal combustion engine of a motor vehicle which prevents the internal combustion engine from being started when the clutch, the gearbox, the brake or a similar device is not in a safe position with respect to the starting procedure.
This system provides safety switches located in the ignition current path and actuated as a function of the clutch position and the load connection. These switches are connected in series and are closed when the internal combustion engine can be started without danger.
U.S. Pat. No. 5,101,802 describes an electronic ignition system for a magneto-ignition internal combustion engine which can be optionally started by motor or manually. In this system, a safety switch in series with the ground connection of the magnet coil is closed, for example, only in a neutral position of the gear-selection switch so that initial induction of the ignition voltage is only possible in the mentioned gear position.
An object of the invention is, therefore, to provide a device for influencing the starting of the internal combustion engine of a motor vehicle with an electronically controlled gearbox, which device has, on the one hand, a high level of imminent safety against unallowable starting of the internal combustion engine and, on the other, leads to a simplification of the electrical installation in the vehicle.
This and other objects are achieved by the present invention which provides a device for influencing starting of an internal combustion engine of a motor vehicle that has an electronically controlled gearbox, an electrically acting interlock that prevents the internal combustion engine from being put into operation when a gearbox status causing a driving force connection is selected, and a starter with an electromagnetic disengagement switch that is suppliable with battery current from an ignition switch during actuation of the starter. The device comprises an electronic engine control unit for at least one of ignition and metering of fuel, with a communicative connection communicatively connecting the engine control unit to the gearbox control. A direct connection is provided from the ignition switch to the electromagnetic disengagement switch for supplying battery current to the electromagnetic disengagement switch without an intermediate disabling switch. A recorder records the position of an element influencing the gear-selection status of the gearbox and transmits a corresponding signal to the gearbox control. The gearbox control acts upon the engine control unit via the communicative connection to disable at least one of the ignition and the fuel metering when the element influencing the gear-selection status of the gearbox is in a position which normally effects a driving force connection through the gearbox.
The signal initiating the disabling of the ignition and/or fuel metering can therefore be transmitted within a serial twin-wire or optical bus log as a datum which normally puts the internal combustion engine out of operation. It is possible to interrogate both the selector lever actuated by the vehicle driver and a gearbox-end control element, by whose change in position changes to the gear-selection status of the gearbox are necessarily initiated directly. A switch, which is therefore electrically only slightly loaded, can be used for this purpose.
By an additional disabling status conductor between the gearbox control system and the electronic engine control unit, which can be provided in practice with practically no complication, a separate disabling signal can be transmitted to the engine control unit independently of and redundant to the previously mentioned serial bus connection between the gearbox control system and the electronic engine control unit. This increases both safety and the ability to recognize faults.
In accordance with the present invention, provision is also made so that where at least one disabling signal is not output to the electronic engine control unit, the gearbox is, in any event, driven into its neutral gear-selection status "N".
In accordance with the invention, it is also possible to dispense with the separate disabling status conductor if, in the presence of a gear-selection status of the gearbox with driving force connection (i.e. not "P" or "N") when the vehicle is stationary, a signal value which normally reports the gear-selection status back to the gearbox control system is altered into an invalid signal value, for example by means of a corresponding switch, this value being discriminated by appropriate means in the gearbox control system and processed to provide a disabling signal which can be emitted to the electronic engine control unit.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.